Conventionally, there are much studies regarding polymerization of an alkylene oxide, especially ethylene oxide, propylene oxide, etc. For example, it is known that a product prepared by reacting a monohydric alcohol further to a product obtained by reacting an organozinc compound to a polyhydric alcohol, or a product prepared by reacting a polyhydric alcohol further to a product obtained by reacting an organozinc compound to a monohydric alcohol (see, for example, Patent Documents 1 and 2) exhibits an excellent catalytic activity for homopolymerization of an alkylene oxide or copolymerization of two or more alkylene oxides and a polymer having a high degree of polymerization can be obtained.
However, there have been noted problems in that production stable on an industrial scale cannot be carried out by these methods, for example, reproducibility of polymerization speed or degree of polymerization of a resulting polymer is poor, resulting in failure to attain a sufficiently high yield, or a polymerized product agglomerates. Moreover, those methods are not fully satisfactory in degree of polymerization. On the other hand, there have been attempted methods of obtaining a polymer reproducibly by using a product prepared by reacting an organozinc compound and a polyhydric alcohol with each other (see, for example, Patent Document 3) as a catalyst in contact with various types of fine particulate metal oxide as a dispersion aid and a nonionic surfactant, but there has been noted a drawback that the operation of catalyst preparation is very complicated.
As a solution to the above-described problems, it is proposed, for example in Patent Document 4, to use as a polymerization catalyst a material prepared by heat-treating within a certain temperature range a product obtained by reacting an organozinc compound with an aliphatic polyhydric alcohol and a monohydric alcohol in a certain equivalent ratio.